Ink jet recording heads form dots on a recording medium by jetting ink droplets through nozzle openings. The ink is provided to a given nozzle opening from a pressure producing chamber, which is itself supplied with ink by a common ink chamber.
Reducing the size of each ink droplet permits an ink jet recording head to be designed so as to print data at extremely high resolutions. It is clear that a greater number of nozzles generally increases printing efficiency. For efficiency, then, the use of smaller ink droplets dictates that the nozzles be arranged densely.
An advantageous nozzle arrangement is a staggered arrangement. In other words, not only are a plurality of rows of nozzle openings provided in a small area, but they also are arranged so that the nozzle openings in one row are positioned in the spaces between the nozzle openings in another row. By staggering the nozzle openings, the recording density of an ink jet recording head can achieve 90 to 180 dpi. If the number of rows of nozzle openings is increased, the recording density, theoretically, can be improved to as high as 360 dpi.
Ink jet recording heads often have a laminated structure. In an ink jet recording head of this type, it is common to use piezoelectric vibrators to cause the ink droplets to be jetted through the nozzle openings. For example, a piezoelectric vibrator exerts a force on a pressure producing chamber so that ink is jetted through the nozzle opening. In designing a laminated ink jet recording head, it is extremely important that the size of the piezoelectric vibrators be minimized. However, since the piezoelectric vibrator must exert a minimum drive force on the pressure producing chamber to cause the jetting of ink droplets, the piezoelectric vibrators cannot limitlessly be downsized.
For the sake of rigidity, certain layers of a laminated ink jet recording head may be made of ceramics. This ensures that the common ink chambers, for example, have high rigidity. A highly rigid layer of this type, however, resonates at a high resonance frequency. The resonance frequency, moreover, is almost equal to the inkjet recording device drive frequency. As a result of this relationship between the resonance frequency and the drive frequency, the quantity of ink in an ink droplet tends to decrease below normal at certain frequencies within the drive frequency range. When the quantity of ink in an ink droplet so decreases, the ink jetting characteristics of the inkjet recording head become unstable. To put it another way, the print quality deteriorates as a result of the decreased amount of ink in a jetted ink droplet.
Approaches to overcome this problem involve placing a thin-walled portion in the common ink chambers, or increasing the fluid resistance of the ink supply ports that connect the common ink chambers to the pressure producing chambers. Adopting these approaches, however, give rise to new problems. In particular, the new problems are that special machining is required, and that the drive speed is decreased.